bug: ion-datetime does not update when the system timezone changes

[mschmermer]

Prerequisites

• I have read the Contributing Guidelines.
• I agree to follow the Code of Conduct.
• I have searched for existing issues that already report this problem, without success.

Ionic Framework Version

v8.x

Current Behavior

I’ve noticed that ion-datetime does not automatically update its timezone when the system timezone changes.

Possible solutions:
1. ion-datetime should automatically update when the device’s timezone changes.
2. Add a timeZone input property to manually set the timezone if needed.

Could you please check this behavior and consider improving ion-datetime’s timezone handling?

Thanks for all the great work on Ionic! 🚀

Let me know if you want any changes or if you’d like me to submit this issue for you! 😊

Expected Behavior

•	ion-datetime continues to use the old timezone.
•	Even though I implemented a custom Capacitor plugin to retrieve the correct system timezone, it has no effect on ion-datetime.

Steps to Reproduce

Steps to reproduce:
1. Open an Ionic app with an ion-datetime component.
2. Change the system timezone (e.g., from Europe/Berlin to America/New_York).
3. Check Intl.DateTimeFormat().resolvedOptions().timeZone to confirm the new system timezone.
4. ion-datetime still displays the old timezone until the app is restarted.

Code Reproduction URL

https://ionicframework.com/docs/api/datetime#time-zones

Ionic Info

Technical details:
• Ionic version: 8
• Capacitor version: 6
• Platforms: iOS, Android
• Custom plugin for timezone update: ✅ Yes

Additional Information

No response